My backup power solution -- critique wanted.

[Ignoramus3934]

A few days ago I started a thread titled "superoversized alternators" on m.s. and a.h.r. My question was how to use an alternator from my pickup truck as al alternative source of emergency power. I do have a diesel generator but it is broken and I need to spend time on it. I suspect that I am missing something trivial with the generator as it looks great and is military surplus bought directly from military.

My primary need for power during power outages would be to supply power to the furnace blower (nat gas), fridges, and some house lighting and maybe TV/Radi.

My solution is as follows: I have a Ferrups FE series UPS. This is a

1.4 KVA model that has a regular gel cell lead acid 12 volt battery as the power storage. By the way, I found that Ferrups UPS on a street, someone simply took it out to the curb. (!)

I would keep that ferrups plugged in and charged. I will also connect

3 gauge stranded wire to the battery posts of the UPS so that the wire can be connected to an outside 12vdc power source. If power goes out, I would connect the furnace to the UPS by means of extension cords (some rewiring of furance would be needed to accommodate it safely). Then to supply more power than is stored in the 12v battery inside the UPS, I would start my pickup, run it at idle speed, and connect the battery posts in the truck to the 3 gauge wires I connected to the UPS battery (see above) with a jumper cable.

Advantages of this setup:

1) Can accommodate surges of power without putting extra load on the alternator, because the UPS itself has a reserve of power in the battery

2) I do not need to buy a separate large capacity inverter, will be using what I already have

3) For brief outages, all I would need is running extension cords to a few freestanding lights. and the furnace.

I am aware that devising means to switch the furnace to alternate source of power, without buying a transfer switch, is tricky. I will try to do something that is safe and to the code. My current inclination is to supply the furnace with a 1 foot cord that would plug into a regular outlet, or the UPS or generator's extension cord.

i

[Ian Stirling]

You can't safely hook together lead acid batteries in different states of charge.

This can cause very large currents to flow. This isn't trivial to fix, unfortunately.

Simple resistance of the cables helps, but it's not 100%, unless you'r dropping a lot of voltage in the cables.

The much safer way is to install a changeover switch. This would switch between external and internal battery. This does need a large switch, capable of safely handling 12V at around

150A.

[Louis Boyd]

They probably carried to the curb and went to get their truck. Bet they were surprised that someone would rip them off.

[Ignoramus3934]

What about jump starting cars then?

Anyway, it is not a bad idea to change over from the internal battery to external, and, I believe, can be done quite easily and safely. I am not 100% convinced that it is completely necessary because people do jump start cars after all. However if I get reasonable doubt as to whether a direct coinnection is safe, I may do a changeover.

i

[Big-T]

Ignoramus3934 wrote:

Something for you to consider. While I am not familiar with your particular make and model of UPS I have used several types.

I have seen older ones where the protected equipment continuously runs off of square wave or modified square wave inverters. These run the input power (from the grid) to keep the battery charged. This type does not do any switching, because your equipment that is plugged into the UPS is always running off the battery.

The later ones I have used run directly off of grid power until they get either a spike or a dip in power and then switch to the UPS inverter power. The ones I have used were sine wave inverters. The difference in quality of this type is the speed in which they can switch. The good ones are very fast. One thing to note is that (at least on the ones I have used) if it is not on and running when the power goes off you can not turn it on after the fact and get any output power. It has to be plugged in and running when the power goes off to switch and produce off grid power. The second and most important thing for your application is these are not continuous duty inverters like the ones designed for off grid power systems. They are generally designed to keep sensitive electronic equipment running for about 15 minutes. This is so if it is only a blip or short outage you can continue to work uninterrupted or if the power does not come back in a few minutes you can shut down gracefully and not crash and loose data. These things get very hot. The battery they come with is designed to be big enough to run the UPS for as long as the internal electronics. If you give it more battery power from an external source you may be exceeding the capabilities of the thing to get rid of the heat it generates. I know of one guy who used his computer UPS in this way during a blackout. The fancy phone system in the office went down and customers could not get through. Not wanting to loose business. He unplugs computer from UPS and runs extension cord to room with the phone exchange equipment. Works great for awhile. Then battery runs low so he takes battery out of his truck and ties it in and it's working great again. That is for another 15 minutes, until he totally melted the electronics in the UPS. A puff of smoke and then a bad burnt electronics smell. He exceeded the design ability of the unit to cool itself. YMMV, Big-T

[Ian Stirling]

<snip>

Not quite.

For some loads they are equivalent. Heaters, and lightbulbs, for example. The problem arises when you try to connect equipment that has a power-factor of other than one. With a 110V mains, the voltage varies smoothly between -155V and 155V, back and forth 120 times per second.

The power factor is a measure of how "in step" voltage is with current. Some loads like induction motors, some sorts of power supplies, ... have the current out of step with the voltage, which means that for a given current (the guts of the UPS tend to be rated by output current) the wattage is less.

For non sine-wave outputs, these sorts of load are even worse.

The music power is pretty much an intentional lie. The VA rating of the UPS is an indication of it's true capacity, and can be sized in exactly the same way as (for example) breakers.

A 110V 20A breaker will run a 2200W or so load with a power factor of one, but a much smaller load with a power factor of 0.5.

It's the same as the UPS.

[Ignoramus3934]

Thanks. I will check tonight if my UPS can be powered in absence of AC power. It does produce sine wave power. It also has a 0ms transfer time.

Ferrups are generally considered to be the best of breed of UPSes, built like tanks. This is not a "consumer grade" product. They are also offered with "extended battery modules", which strongly suggests to me that they are designed to run off battery power continuously.

They also have a 150% surge capacity even when running on the inverter.

``The Powerware FERRUPS UPS deliver unmatched reliability in configurable power protection for computers and telecommunications equipment. Patented Ferro resonant technology delivers "bulletproof" power protection and is ideal for banking and security systems, manufacturing process control, servers, and telecommunications equipment''

i

[Ignoramus3934]

Thanks Ian.

i

[Big-T]

Great. If they are designed properly for continuous duty with heat sinks and cooling fans for airflow then you should be good to go. I've just seen too many that were not. Big-T

[Ignoramus3934]

Thanks, I know what you mean. Hard to build cheap stuff to sell to uninformed customers and that also works very well. Ferrups are generally fairly expensive but they have a lof of features. That one surely has a built in fan, I saw it when I took the UPS apart.

One last concern that I have is that when my truck engine is running, the voltage reads as 14 volts, not 12.4 or so as it would be from just a battery. Can it damage the inverter?

i

[Kevin Ricks]

They do it this way partly for marketing and partly because when something is stated at so many VA then the user/installer can figure out what the operating current will be based on the local input voltage. The input voltage can vary depending on where you install the unit. So on a 1400 VA unit if the input voltage is 120 V the AC INPUT current is 11.6 Amp. If the AC input is 115 V then the current used is 12.2 Amps etc. In the past the VA was used primarily on motors and compressors and such. If not VA then the manufacture would have to put on a huge label with several lines of text: If

110 V then x Amps.. if 115 V then y Amps.. if...etc.... If they use a VA rating then just a few charters will tell all. Now for the UPS it is not really necessary to use the VA, but it gives you a bigger number to look at for marketing or advertising . Just like the vacuum cleaners manufactures that advertise a 12.5 Amp Max... It has nothing to do with the efficiency of the vacuum cleaner itself. How much power are the head lights cornering lights, turn signals..... etc use? For the UPS you must subtract the current used by the electronics, charging circuit etc. to come up with the usable output current/power rating. A label on the back should say. (The 1400 VA UPS should give about 900 to 1000 Watts).

Finally for the OP the charging circuits for the sealed lead acid batteries are different than for the relatively crude charging circuit used for automobile batteries. If you didn't have a isolation switch then when the AC power is restored, the UPS will attempt to charge the auto battery which may demand more current than the UPS can give. (but I guess you could leave the UPS unplugged from the AC). If the car engine is running the UPS might not like the alternator output? One more very important issue. What DC voltage does the UPS really use 12V or 24V or more? Pull the batteries in the UPS and verify how they are wired. Or use a voltmeter. Do not rely on the voltage label on an individual battery. It is probably using from 2 to 4 batteries in 24 volt series/parallel arraignment. You would need to use 2 or more car batteries to provide that voltage. Kevin

[Ignoramus3934]

Thanks Gunner. You convinced me. I will add a changeover switch. I could just make something on my own. What are those switches called if I was to search for them?

Thanks.

i

[Ignoramus3934]

gunner, I found the answer to my question. thanks.

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[Vaughn Simon]

Those ferro-resonant transformers have rather large core losses. Just allow it to idle for a couple of hours and note the heat being blown out by the fan. I would leave the unit UNplugged except when you need it and keep the battery up with a good smart trickle charger.

Vaughn

[Bob Adkins]

Some things I learned about surge protectors: The charger is very slow and gentle, and usually charges in the low 13v range. I suppose this is to increase battery life. Therefore, the battery will probably not deliver its rated AH. The battery is most likely an LC type, not gel. That's a good thing.

Bob

[Ignoramus3934]

thanks Vaughn, it is not a bad idea. I will have the isolation switch anyway, thanks to gunner's and others' tips, so I can easily accommodate a trickle charger which I already own.

Quick question... Will that ferrups UPS charge any capacity battery, or only the specific one that comes with it?

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[Stormin Mormon]

Is it possible you are comparing "watts per hour" which would be like the number on a light bulb "95 watts per hour" versus "watts total storage".

A 300 watt system would have a 300 watt inverter.

However, it might be connected to a 1,000 VA battery.

[Sylvan Butler]

And then when the guy came that was supposed to pick it up, she and he got a suprise together.

sdb

[Jim Yanik]

Ignoramus3934 wrote in news:bhr093$jod$ [e-mail]:

It shouldn't;lead-acid batteries 'full-charge' state is 13.8V to 14.xV.

12V is 'charge-depleted' state.

[Nick Pine]

Utter bullshit. Learn the difference between power and energy.

Nick